1. Field of the Invention
The present invention relates to robotic cart pulling vehicles for automated hauling of materials indoors. More specifically, the present invention relates to a cart pulling deduced reckoning guided mobile robot system.
2. Background of the Invention
Robotic and automated vehicles for delivering or transporting material indoors have been developed and utilized in a number of applications. One well-known application is the automated mail delivery vehicles and robots. An example of such a mail delivery vehicle is manufactured by the Mailmobile division of Bell and Howell. Rather than being an independent robotic vehicle, this is an automatic guided vehicle following a prepared track, such as a painted ultraviolet track positioned on the floor. Another example is produced by FMC which manufactures an automated transport and logistics integration system, referred to as ATLIS, for moving specially designed carts in indoor environments, such as hospitals. To pick up a cart, the ATLIS vehicle positions itself under the cart, the deck of the vehicle is equipped with an electric lift which extends to raise the cart from the floor. The ATLIS system is generally a wire-guided system requiring a guide wire to be permanently installed in the floor.
In the hospital environment, a company referred to as Helpmate Robotics developed a robotic courier for hospitals. The robotic courier was essentially a wheeled cabinet. This hospital robotic courier is currently being offered by the Pyxis division of Cardinal Heath, Inc. The robotic courier has many disadvantages, the first of which is that it is overly expensive, and a second is that it is only useful for transporting materials that can fit in the associated cabinet installed with the robot.
A wide variety of prior art robotic and automated vehicles are discussed in the patent literature. For example, U.S. Pat. No. 4,746,977 to White is directed to a remotely operated steerable vehicle. U.S. Pat. No. 4,871,172 to Kanayama is directed toward a mobile robot and a control therefore. U.S. Pat. No. 5,488,277 to Nishikawa et al. discloses a collection of mobile robots and a control station for the plurality of mobile robots. U.S. Pat. No. 5,175,480 to McKeefery et al. is directed toward an automated guided vehicle. U.S. Pat. No. 5,461,292 Zondlo discloses a remote controlled two-wheeled lawn mowing vehicle. U.S. Pat. No. 5,545,960 to Ishikawa is directed toward a mobile machine following a predetermined path. U.S. Pat. No. 5,819,863 to Zollinger et al. is directed toward a robotic vehicle including a support structure. U.S. Pat. No. 5,709,007 to Chiang discloses a remote control vacuum having a remote control drive unit or cart to which a portable vacuum unit is removable attached.
Further the patent literature discussed a wide variety of navigational, error control, and obstacle detection systems such as discussed in the following patents that are incorporated herein by reference.
U.S. Pat. No. 5,276,618 to Everett, Jr. is directed toward a doorway transit navigational referencing system for a robot vehicle. This system utilizes a plurality of sensors for sensing known reference objects to obtain orientation information.
U.S. Pat. No. 5,324,948 to Dudar et al. discloses a robot following a predetermined path and uses the collection of a series of distinct data points between the sensor and a wall in order to recognize the object as a wall. Additionally, the patent discloses that if a door or other wall feature is found, the robot will ignore the new data points and use ded-reckoning until a valid “wall” is found.
U.S. Fat. No. 5,402,344 to Reister et al. is directed toward a method for independently controlling steerable drive wheels of the vehicle with two or more such wheels. The system provides a method for determining the wheel slip associated with a given wheel.
U.S. Pat. No. 5,548,511 to Bancroft discloses a robotic cleaning apparatus in which the robot measures and records the distances to the left and right boundaries as it travels to determine or map the area. Subsequent to mapping the area, it will determine the path for cleaning the area with the robot following a predetermined path in such cleaning. The Bancroft patent does disclose that encoders provide ded-reckoning navigation while the sensors provide corrections to errors caused by, for example, slippage of the wheels. The precise correction method utilized is not discussed. Additionally disclosed is that the sensors can be advantageously used to follow variations in the boundary of the area that deviate from dimensions measured in the learning phase and to avoid obstacles in the area. The Bancroft patent additionally discusses dealing with areas or variations by using the mode of the measurements obtained by the sensors, that is the value of the measurement that occurs most often. Additionally, the robot ignores measurements that are greater than a maximum range of the sensor.
U.S. Pat. No. 5,556,356 to Kim discloses a mobile robot incorporating a position correcting system. Included in the system is a distance detecting mechanism or sensor detecting the distance of separation between the robot and a separate positioning correcting mechanism positioned within a wall. The position correcting mechanism in the wall can include an infrared receiving unit and a transmitting unit which is selectively activated by the robot as is passes to send appropriate control compensating signals to the robot.
U.S. Pat. No. 5,559,696 to Borenstein discloses a mobile robot with an internal positioning error correction system utilized for correcting non-systematic deduced reckoning errors and discloses a robot with a trailer hitch connected to the center of the robot.
U.S. Pat. No. 5,652,489 to Kawakami is directed toward a mobile robot control system wherein the robots move on a predetermined route in a given area including optical detection sensors.
U.S. Pat. No. 5,680,306 to Shin et al. discloses a robotic vehicle primarily utilizing global positioning systems (GPS). The patent additionally discloses the use of deduced reckoning to supplement the GPS system.
U.S. Pat. No. 5,684,696 to Rao et al. discloses a system and method for enabling an autonomous vehicle to follow a desired path. The system utilizes a combination of a GPS and an initial reference unit (IRU) integrated together.
U.S. Pat. No. 5,687,294 to Jeong is directed toward a control system for a mobile robot including obstacle detection and correction of positioning and directional errors.
U.S. Pat. No. 5,739,657 to Takayama et al. is directed toward a control system for controlling the motion of an omni-directional robotic vehicle.
U.S. Pat. No. 5,819,008 to Asama et al. is directed toward a mobile robot sensor system for a system of multiple robots in a given environment. The robots utilize infrared sensors for communicating with other robots for avoiding other roots in the environment.
U.S. Pat. No. 5,942,869 to Katou et al. discloses an automated robotic vehicle utilizing caterpillar treads. Additionally disclosed is the use of supersonic or ultrasonic sensors for obstacle detection.
U.S. Pat. No. 6,041,274 to Onishi et al. is directed toward a positional deviation detecting device for a robot or working machine which utilizes a pick-up sensor for detecting the image on a floor.
The above discussed prior art does not effectively provide for a cart pulling or cart pulling robotic vehicle that would be useful for hauling materials on a variety of carts or wagons indoors. A cart pulling ded-reckoning guided robotic vehicle is disclosed in U.S. Pat. No. 6,046,565 (hereinafter “the '565 patent”) that is also incorporated herein by reference. The '565 patent discloses a robotic vehicle with a deduced reckoning positioning system having a center mounted harness, or attachment mechanism, on the robot body for coupling a cart or wagon to be pulled thereby. The '565 patent teaches that the system calibrates the absolute position of the robotic vehicle relative to a fixed reference marker, such as a wall, to eliminate the accumulated error in the calculated position of the robotic vehicle. Additionally, the '565 patent discloses that a single reference wall may be used to eliminate the error in selected two parameters. With regard to the attachment mechanism or harness, the '565 patent suggests that the ratio of the height of the harness joint above the floor to the axle width should be as low as possible to better approximate the ideal planar situation. The '565 patent does not discuss the attachment mechanism further.
All of the above-discussed prior art has substantial disadvantages. It is the object of the present invention to improve upon the prior art and provide a cart or wagon pulling deduced reckoning guide mobile robot system useful for industrial applications, such as in hospitals and like. In this regard, the present application can be considered an improvement over some of the fundamental concepts disclosed in the '565 patent.